docs(460): drop the "clean at rest" overstatement from the test header

Follow-up to the cold review of 615e00a. The record was corrected to say only
that no NEW sentinel rows are created, but the test file's header still carried
the disclaimed "the data is clean at rest for every provider" claim — sitting on
the very test that supposedly proved it. It now states what the tests actually
pin, and names what they cannot speak to (rows written before this change, which
keep the sentinel and are covered only by the read coercion).

Also corrects docs/testing.md's ErsatzTV.Core.Tests count (543 -> ~650 measured;
the neighbouring Scanner.Tests cell is corrected in #602 instead, to keep the two
open PRs off the same line).

ErsatzTV.Tests/Integration/MediaSourceRepositoryDisableSyncTests.cs

@@ -12,7 +12,9 @@ namespace ErsatzTV.Tests.Integration;
 // ersatztv#460: the disable-sync (remove-and-recreate) flows used to stamp the 0001-01-01 MinValue
 // sentinel into Library.LastScan. #409 fixed the READ side (the API coerces the sentinel to null and a
 // migration cleaned historical rows), so the wire contract was already correct — these tests pin the
-// WRITE side, so the data is clean at rest for every provider and no new sentinel rows are created.
+// WRITE side for every provider, so no NEW sentinel rows are created. They do not (and cannot) speak to
+// rows already written before this change: those keep the sentinel at rest and are covered only by the
+// read-boundary coercion, since this ships no second cleanup migration.
 [TestFixture]
 public class MediaSourceRepositoryDisableSyncTests
 {

docs/testing.md

@@ -8,7 +8,7 @@ before adding tests, not just `docs/contributing.md` §8 (which now just points
 | Project | Covers | Notes |
 |---|---|---|
 | `ErsatzTV.Tests` | API controllers + MediatR handlers | In-memory SQLite fixture: a shared `SqliteConnection("Data Source=:memory:;Foreign Keys=False")` kept open + `EnsureCreatedAsync()` (**not** full migration replay) + `PRAGMA foreign_keys=OFF`, then seed; a tiny `IDbContextFactory` wraps `new TvContext(...)`. ~1,870 tests (approximate on purpose — an exact count goes stale on every PR that adds one; the previous hardcoded 828 was off by over a thousand). |
-| `ErsatzTV.Core.Tests` | Domain logic, scheduling, IPTV/XMLTV generation | References `ErsatzTV.Application` directly — there is no separate `Application.Tests` project. 543 tests + 1 skipped under `TZ=UTC` (the Block playout golden additionally skips under a non-UTC `TZ`; see Golden-file nets). |
+| `ErsatzTV.Core.Tests` | Domain logic, scheduling, IPTV/XMLTV generation | References `ErsatzTV.Application` directly — there is no separate `Application.Tests` project. ~650 tests + 1 skipped under `TZ=UTC` (the Block playout golden additionally skips under a non-UTC `TZ`; see Golden-file nets). |
 | `ErsatzTV.Scanner.Tests` | Library scanning: scan handlers, folder scanners, NFO readers | Handler tests substitute the folder scanners + `ILibraryRepository` and assert the resulting repository writes (e.g. `ScanLocalLibraryHandlerTests` pins which `LastScan` levels a scan records — ersatztv#264). Fakes/`Testably` back the file-system-facing scanners. ~1,485 tests (approximate on purpose — an exact count goes stale on every PR that adds one). Additionally contains `Core/FFmpeg/TranscodingTests` — `[Explicit]` + `[Combinatorial]`, so it never runs in CI or a plain `dotnet test` (it needs real ffmpeg/hardware) and contributes 0 to that count; run it by name when touching the transcoding pipeline. |
 | `ErsatzTV.Architecture.Tests` | Layering rules via NetArchTest.eNhancedEdition | Core↛Infra/App/EF; FFmpeg↛all; App↛concrete providers. 5 tests. See `docs/contributing.md` §1. |
 | `ErsatzTV.FFmpeg.Tests` | FFmpeg command construction | Build a pipeline, assert the exact rendered arg string (`PipelineBuilderBaseTests.cs`). |